Hereinafter, conventional fabrication methods are to be described with reference to a few drawings for better understanding of the background of the invention.
FIG. 1 shows schematically a conventional hydrogen plasma treatment apparatus. As shown in this figure, the conventional apparatus comprises a vacuum chamber 1 in which an external RF power source 2 enables a pair of cathodes 3 to generate a radio frequency, and an anode that consists of a substrate 4 supported by a supporter 5 are provided.
In the apparatus, a gas supply system 6 which supply hydrogen (H.sub.2) gas to the space between the pair of cathodes of the vacuum chamber 1 is set at the exterior of the chamber to control the quantity of hydrogen whereas an exhaust system 7 which appropriately maintains the pressure of the vacuum chamber 1 at working pressure is set at one side of the chamber.
Description for the processings with the above-mentioned hydrogen plasma treating apparatus will be given next.
Hydrogen (H.sub.2) gas is supplied in the quantity of approximately 10 to 500 sccm into the vacuum chamber 1 in proportional to the size of the substrate 4 or the vacuum chamber 1. While the temperature of the substrate is maintained in a range of approximately 250.degree. to 350.degree. C., reaction pressure is kept in the range of a vacuum of approximately 0.1 to 1 torr by controlling the exhaust system 7.
Under such conditions, the power which is supplied to the vacuum chamber in the quantity of approximately 0.05 to 1 W/cm.sup.2 from the RF power source 2 forces the hydrogen (H.sub.2) to be separated into plasma which is then diffused into a semiconductor film on the substrate 4, resulting in the hydrogenation of the semiconductor film. At this time, the control of the apparatus is determined by the concentration of hydrogen radical (separated into plasma) on the surface of the substrate 4 and the hydrogen diffusion rate which is dependent on the substrate temperature.
Turning now to FIG. 2, there is shown another conventional apparatus for semiconductor hydrogenation treatment, which employs light for the hydrogenation. As shown in this figure, this apparatus comprises a chamber 1 in which a substrate 4 supported by a substrate supporter 5 is provided in a lower portion, a gas supply system supplying gas such as H.sub.2 or Hg in a constant quantity, an exhaust system 7 keeping the degree of vacuum within the chamber 1 constant, dependent on the working of a vacuum pump, a quartz window 8 mounted on the upper portion of the chamber, and a low pressure mercury lamp 9 illuminating the chamber through the quartz window 8.
In such apparatus, hydrogen (H.sub.2) and mercury (Hg) gases are, at the same time, supplied from the gas supply system 6 into the vacuum chamber 1 at constant flow rates, respectively. Illumination using ultraviolet rays with wavelengths of 184.9 and 254 nm causes Hg electrons to enter to an excited state (Hg.sup.*) which, in turn, decomposes H.sub.2 gas into radicals. The hydrogen radicals diffuse into a semiconductor film on the substrate 4 to hydrogenate it. The apparatus is controlled by the concentration of hydrogen radical on the surface of the substrate and the hydrogen diffusion rate which is dependent on the substrate temperature. The H.sub.2 concentration is determined by the partial pressures of H.sub.2 and Hg within the vacuum chamber 1.
The conventional apparatuses for the treatment of semiconductor hydrogenation and methods according to the same show problems as follows: first, since the hydrogenation processes are carried out within the vacuum chamber 1, an exhaust system must be required; second, accordingly, the high cost of equipment is needed due to the high priced chamber and the exhaust system; third, the time for treating the substrate is lengthened because processes are carried out in a vacuum state; fourth, if the apparatus shown in FIG. 1 is used in a of a process which is mainly performed under atmospheric, pressure time needed to form a vacuum within the vacuum chamber becomes a factor that lowers the productivity; fifth, since the apparatus described with reference to FIG. 2 uses mercury (Hg), there occurs pollution problems; sixth, in case that a large substrate is made, it is required to make the quartz window 9 passing the light irradiated from the low pressure mercury lamp 9 large as well; and finally, since the low pressure mercury lamp is unable to uniformly large area, it is difficult to make semiconductors with high quality.